1. Field of the Invention
The present invention relates to a recording apparatus for recording input record data in accordance with a predetermined recording scheme.
2. Related Background Art
FIG. 10 shows a configuration of a prior art page printer such as a laser printer. As shown, in the prior art printer, a configuration to connect all devices to one system bus 5 was standard. In FIG. 10, a CPU 1 for controlling the entire system, an interface 2 for connection with a host computer, a system memory 3, an image generation unit 8 for generating a bit map image in accordance with an input character code and a printer language and a printer interface 9 for controlling a recording mechanism (printer engine) 10 are connected to the system bus 5.
In such a configuration, the respective units interfere with each other due to the collision of data on the system bus and the performance is lowered.
The page printer comprises a video controller and a printer engine. The video controller receives print data described in a printer language from a host computer or the like and develops the print data into image data represented by a dot image matrix. In order to store one page of image data, a large memory capacity is required in the printer. As the sheet size or the resolution increases, the number of bits necessary for the memory increases. In order to reduce the memory capacity, a band buffer technique is often used. In the band buffer technique, a page corresponding to the print image is divided into bands in a sheet feed direction. A plurality of band buffers are cyclically used for each output page, and the developing process for one band buffer and the transmission process of the image data from another band buffer to the printer engine are performed in parallel. Usually, the printer engine of an electronic photographic printer such as the laser printer cannot be stopped in the course of the printing of one page. When such a printer engine is used, the developing process takes too much time to prepare the image data to be shipped to the printer engine. Within a record time of one record band, the generation (development) of the image of the next band must be completed. When the amount of print data is large or complex, the generation of the image is not completed in time and an overrun error is unavoidable.
In FIG. 11, symbols A, B, C, . . . indicate record bands (record areas) on a record sheet which is a recording medium, and each section designated as "record data transfer" indicates a section to transfer data of a corresponding band from the image generation unit 8 to the printer interface 9. Each section designated as "image generation" indicates a section to generate image data by the image generation unit 8.
In the prior art, as described above, sufficient image generation velocity for the recording speed of the recording mechanism cannot be attained depending on an operation status, and overrun may occur or throughput may be lowered. Accordingly, recording resolution is reduced in preparation for the overrun or an image memory capable of storing a full page of image data is attached and the entire image data is developed in the image memory before it is recorded.
However, in order to attach the image memory capable of storing the full page of image data, an increase of the cost of the system is unavoidable or a user has to add an image memory supplied as an optional part.
Further, when the resolution is reduced, the recording quality is necessarily lowered.
Further, since the bus for memory accessing is shared with the CPU 1, the image generation unit 8, the printer interface 9 and other I/O devices, when the data amount increases, the performance is significantly lowered due to the traffic on the bus.